It is known to prepare bisphenols, e.g., diphenylolpropanes, by reacting, in a reaction zone, at least 2 moles of a phenol, e.g., phenol itself, with a carbonyl compound, e.g., acetone, at a temperature of from 40.degree. to 95.degree. C., in the presence of an acid exchanger, e.g., a sulphonated ion-exchange resin, e.g., see British Pat. No. 849,965.
The reaction zone effluent may be worked-up in a various ways to recover the bisphenols therefrom. For example, substantially all of the unreacted carbonyl compound and water may be removed from the reaction zone effluent and the bisphenols recovered from the remainder of the reaction zone effluent.
One disadvantage of the known process is that undesirable compounds are formed during the working-up which contaminate the recovered bisphenols. It is not possible to identify positively these undesirable compounds but their presence may be detected by high performance liquid chromatography as hereinafter described.
It has now been found that the formation of these undesirable compounds is substantially reduced if the reaction zone effluent is contacted with an acid ion exchanger in metal salt form and/or a weak base ion exchanger.